1. Field of the Invention
The present invention relates to a solar thermoaccumulator. More particularly, the present invention relates to a solar thermoaccumulator of the type including a plurality or battery of closed-circuit vacuum heat pipes that transfer heat to a circuit to be heated.
2. Prior Art
Apparatuses capable of collecting solar energy and utilizing it for industrial and/or domestic purposes are already known. In particular, there are presently known and increasingly are being developed so-called solar panels, designed for heating water in houses or community facilities such as: hotels, gymnasiums, barracks, camping grounds, and the like. Such solar panels are substantially designed to function according to the process that exploits the physical law by which hot fluids naturally rise, while cold fluids tend to descend in the opposite direction. Some types of flat plate collectors or solar panels are constituted of flat, blackened, metal containers in whose inside a primary fluid flows in coiled pipes. Such panels are insulated at the bottom to prevent convection heat losses, include top blackened glass panels, and are so oriented as to ensure the perpendicularity of their surface with respect to the average direction of the sun""s rays.
Solar rays, both direct and diffuse, going through the thickness of glass, heat the metal surface of the connector and, as a consequence, also the fluid flowing in the coils. The primary fluid, once heated, flows upwards, always due to natural convection (and sometimes also due to forced convection, such as when pumped), travels a circuit that includes a heat exchanger and heats a fluid, typically water, contained in an accumulation reservoir connected to the distribution system.
These apparatuses, although functioning according to a valid principle, have a limited yield of approximately 50% which, although obtained by exploiting the entirely cost-free resource of solar energy, is actually cost disadvantageous when one considers amortization of the high capital costs of the panels themselves.
Solar collectors that utilize the solar pipe technique, which have a higher yield are also known. Such solar pipes include an absorbing plate bonded to a heat pipe, with the assembly being sealed within an evacuated glass pipe, and the heat pipe being coupled to a condenser. Solar radiation striking the plate is absorbed and then transferred as thermal energy to the condenser. The absorbing plate is coated with a special high efficiency selective coating, which ensures the maximum radiation absorption and minimum thermal radiation losses. Heat, which cannot scatter due to the internal vacuum condition, is transmitted without appreciable scattering to an adjoining tubular body, provided with an intermediate wall that separates the delivery circuit from the return circuit of the primary fluid. By exploiting the same physical principle of upward natural circulation of hot fluids from down upwards, and orienting the collecting plates of the solar pipes inclined and perpendicular with respect to the average direction of the sun""s rays, the heated primary fluid can be exploited in a different way. In one case, the upper part of each solar pipe includes hydraulic taps through which the heated fluid is connected to a heat exchanger that heats the water contained in an accumulation reservoir that is, in turn, connected to the distribution systems. In another case, the upper accumulation bulbs of the solar pipes are, alternatively, adheringly engaged, with heat transmission by convection and conduction, in corresponding profiled niches, obtained on the same piping of the circuit of the heat exchanger.
Although the adoption of solar pipes has allowed the realization of marked increases in yield and efficiency, and has allowed the development of solar panels even in regions with reduced sun exposure, the present configuration of such units is still complex and expensive from the point of view of construction, installation, and maintenance. A further drawback lies in the fact that present solar panels have a limited capacity.
Accordingly, one object of the present invention is to eliminate the above drawbacks. More particularly, it is a further object of the present invention to provide a solar thermoaccumulator, which, besides having high thermal yields and efficacy, is easily realizable and has a very reduced cost to manufacture.
According to the present invention, these and still other objects are achieved by a solar thermoaccumulator that includes a plurality or battery of closed-circuit vacuum solar pipes, with each pipe being coupled to a heat accumulation bulb or condenser, a reservoir containing a fluid to be heated, circumscribed by a shell and provided with fluid feeding pipes and discharge pipes, and a means for transferring heat from the heat accumulation bulbs to the fluid to be heated, wherein the heat accumulation bulbs or condensers are mounted on the lower surface of the shell of the reservoir containing the fluid to be heated.
According to a preferred embodiment of the present invention, the reservoir containing the fluid to be heated is provided with a peripheral, annular, enveloping chamber having an air space, whereto the primary conductive liquid is caused to flow and the heat accumulation bulbs or condensers are immersed in said primary conductive liquid.
According to another preferred embodiment of the present invention, the lower surface of the reservoir; containing the fluid to be heated, is provided with tubular, parallel and aligned tangs, and the heat accumulating bulbs or condenser are placed in direct thermal conduction touch with the tangs.
The reservoir containing the fluid to be heated may be a single reservoir, having preferably a horizontal orientation, or it may be associated with other reservoirs, horizontal, parallel aligned and communicating with each other through slits or longitudinal ports.
The advantages achieved by the solar thermoaccumulator of the present invention lie essentially in that the connections of the accumulation bulbs of the closed-circuit vacuum solar pipes with the reservoirs are much simpler to construct and more accessible for both the assembly and maintenance operations, and besides the mutual association of heat transfer is caused to be more effective, with a higher yield. Another advantage lies in that, as the minimum overall dimensions increase, marked increases in the heated fluid capacity are obtained.